Instrument and method for applying surgical fasteners

ABSTRACT

An instrument for applying fasteners such as bioabsorbable skull rivets, having a piston coaxially received within a housing. The piston has a tip at its distal end and the housing has a distal end sized to receive the tip and also to receive a portion of on of the fasteners. A slit in the housing allows it to flex and accommodate the fastener.

Priority is claimed to Provisional Application Ser. No. 60/234,491filing date Sep. 22, 2000.

FIELD OF THE INVENTION

The present invention relates to an apparatus and method for applyingsurgical fasteners, and in one particular aspect to such an apparatusand method for driving rivets to secure cranial plates.

BACKGROUND

It is known in the art to apply fasteners for attaching sutures, boneplates, and connective tissue. The fastener is inserted into a hole in abone and generally through some application of force is caused toexpand. One particular method for driving a fastener is disclosed inU.S. Pat. No. 5,398,861 by Green which discloses a spring loadedretractable piston and a pivotable trigger device for releasing thepiston and allowing it to drive forward and drive home a fastener. Onedisadvantage of this device lies in the difficulty in grasping thedevice and firing the trigger simultaneously.

SUMMARY OF THE INVENTION

An instrument according to the present invention for applying a surgicalfastener comprises an elongated body having proximal and distal ends. Apiston is axially moveable within a bore within the body, the pistonhaving a distal end adjacent the body distal end and a slit through thebody to the bore, the slit extending a distance axially from the bodydistal end. The bore at the body distal end is sized to snugly receive aportion of the fastener therein and the slit allows the body tocompressively hold this portion of the fastener. The inside diameter ofthe bore prior to cutting the slit is preferably about 0.0595 inches andthe outside diameter of said portion of the fastener is about 0.0590inches and the slit is about 0.014 inches wide. Preferably, the slit hasa distal end at the body distal end, and an opposite proximal end, theproximal end of the slit opening into an aperture wider than the slitwhereby to reduce stress on the body at the slit proximal end.Preferably, a spring urges the piston toward the body distal end and areleasable catch on the body restrains distal movement of the pistonwhereby release of the catch allows the spring to move the pistondistally to impact and apply the surgical fastener.

A method according to the present invention provides for holding asurgical fastener within an instrument for applying the fastener. Themethod comprises the steps of: providing an instrument comprising anelongated body having proximal and distal ends, a piston axiallymoveable within a bore within the body, the piston having a distal endadjacent the body distal end, and a slit through the body to the bore,the slit extending a distance axially from the body distal end; andpushing a portion of the fastener into the bore at the body distal end,the body contracting about portion of the plug to hold the plug withinthe body. To apply the fastener the piston is moved distally to engageand thereby apply the fastener. Preferably, the fastener comprises aplurality of axially extending leaves and a cylindrical plug adjacentthereto and the method further comprising the step of pushing the plugwith the piston between the leaves to spread the leaves and expand thefastener. Preferably, the fastener is formed of a bioabsorbablematerial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of an instrument for applying surgicalfasteners according to the present invention;

FIG. 2 is a section view taken along lines 2—2 of FIG. 1;

FIG. 3 is a perspective detail view of a release button for theinstrument of FIG. 1;

FIG. 4 is perspective view of a fastener for using in the instrument ofFIG. 1;

FIG. 5 is a section view taken along lines 5—5 of FIG. 4;

FIG. 6 is a top plan view of a plate to be applied using the fastener ofFIG. 4;

FIG. 7 is a top plan view of a tray holding a plurality of the fastenersof FIG. 4;

FIG. 8 is a sectional view taken along lines 8—8 of FIG. 7;

FIG. 9 is a detail sectional view taken along lines 9—9 of FIG. 7;

FIG. 10 is a perspective view of the tray of FIG. 7;

FIG. 11 is a sectional view taken along lines 11—11 of FIG. 1;

FIG. 12 is top plan view of a drill for drilling holes in a skull toreceive the fastener of FIG. 4; and

FIG. 13 is a sectional view taken along lines 13—13 of FIG. 12.

DETAILED DESCRIPTION

Referring now to the drawings, FIGS. 1 and 2 illustrate a rivet applier10 according to the present invention. It comprises in general anelongated cylindrical body 12, a piston 14 restrained by a spring 16 anda release mechanism 18. An axial bore 20 passes through the body 12 andhas varying diameters. At a proximal end 22 of the body 12 a firstportion 24 of the bore 20 has a relatively large diameter to accommodatethe spring 16 which is coiled about the piston 14 within the firstportion 24. Intermediate portion 26 of the bore 20 has an intermediatediameter closely matched to the diameter of the piston 14.

At a distal end 28 of the body 12 a distal portion 30 of the bore 20 hasa narrow diameter to accommodate a hardened setting pin 32 whichprojects axially from a distal end 34 of the piston 14. Preferably, thesetting pin 32 is an integral part of the piston 14, but canalternatively be a separate piece affixed to the piston 14.

The spring 16 is caged between a flange or retaining clip 36 about thepiston 14, and a washer 38 and retaining clip 40 at the body proximalend 22. The piston 14 passes outwardly of the body 12 through the washer38 and retaining clip 14.

At a proximal end 42 of the piston 14 a handle 44 is provided for manualretraction of the piston 14. The proximal half of the body 12 isprovided with flutes 46 for enhancing gripability and an axial flange 48is provided near the body distal end 28 also to enhance gripability andmaneuverability of the rivet applier 10. A flat 49 on the flange 48inhibits rotation of the rivet applier 10, thereby reducing thelikelihood that it will roll off of a surface upon which it is placed.The body distal end 28 tapers to a narrow tip 50 to allow more precisedirection of the instrument 10. The set pin 32 is fixed within a coaxialbore 52 in the piston distal end 34.

A circumferencial groove 54 surrounds the piston 14 near its distal end34. A radial bore 56 passes into the body 12 adjacent the groove 54 andextends beyond the bore 20 but does not completely penetrate the body12. Turning also to FIG. 3 the release mechanism 18 comprises a releasebutton 58 received within the bore 56 and a the coil spring 60 betweenan end of the bore 56 and the button 58 which biases the buttonoutwardly of the bore 56. The button 58 has a radial bore 62 throughwhich passes the piston 14. A radial flange 64 within the bore 62 isadapted to engage the circumferential groove 54 on the piston 14.

When the handle 44 is retracted, causing the piston 14 to retractproximally, the flange 64 rides over the surface of the piston 14 untilit encounters the circumferential groove 54 into which the spring 60causes the flange 64 to slip. This action locks the piston 14 in aretracted position as its distal motion is restrained by the abutment ofthe flange 64 and groove 54. Inward pressure applied to the button 58causes the flange 64 to disengage from the circumferential groove 54 andallows the spring 16 to drive the piston 14 forward or distally. Thiscauses the setting pin 32 to move distally to a position flush with thedistal end of the body 12.

FIGS. 4 and 5 illustrate a rivet 66 for use with the instrument 10. Therivet 66 comprises a round head 68 from which extends axially 3 leaves70. A cylindrical plug 72 extends axially from the head 68 in theopposite direction and is frangible connected to the head 68 through afrangible connection 74. The surfaces of the leaves 70 are curved sothat the combination of the three leaves 70 provides an overall tubularconfiguration. Application of force in the axial direction applied tothe plug 72 breaks its frangible connection 74 with the head 68 andallows it to drive axially into a position between the leaves 70 thuscausing the leaves 70 to spread.

FIG. 6 shows a cranial plate 76 for placement on a skull of an patient,either human or animal (not shown). It comprises a flat planar body 78having a plurality of circular extensions 80 therefrom, each of whichhas a countersunk bore 82 therethrough. A tag 84 extends from the plate76 and serves several functions. The tag 84 may contain model number,size, material, date and other pertinent information as well as showingwhich side of the plate 76 is to face upwards away from the patient'sskull (not shown). It also provides a purchase location for a user'shand to hold and manipulate the plate 76 during placement. A frangibleconnection 86 between the tag 84 and the remainder of the plate 76allows easy removal of the tag 84 from the plate 76 after placement ofthe plate 76. Many other configurations of plates will be apparent tothose of skill in the art.

Turning to FIGS. 7 to 10, the rivets 66 are disposed for use in a tray88. The tray 88 comprises a base 90 having a downwardly extendingperipheral wall 92 and a plurality of wells 94 therein. Preferably, thewells 94 penetrate the base 90. A plurality of the rivets 66 residewithin the plurality of the wells 94 with their plugs 72 facing upwardlyout of the wells 94. A film cover 96 adheres to the base 90 over atleast the area of the base 90 comprising the wells 92 to hold the rivets66 within the wells 92. The film cover 96 preferably has slits 97,scorings or some other weakness at each of the wells 92 to allow accessto the rivets 66 through the film cover 96 by the instrument 10 (notshown in FIGS. 8 to 10), although a suitable material allowing accesstherethrough without slits or the like may be employed.

FIG. 11 illustrates the distal tip 50 of the instrument body 12. Itcomprises at least one axial slit 98 extending proximally from thedistal end 28 and terminating in an aperture 100. A chamfer 102 is alsoprovided at the distal end of the bore 20. In one preferred embodiment,the plugs 72 of the rivets 66 (FIG. 4) have an outside diameter of0.0590 inches (1.50 mm), the bore distal portion 30 has an insidediameter of 0.0595 inches (15.1 mm) and the outside diameter of the tip50 is 0.140 inches (3.56 mm). The slit 98 allows the material of the tip50 to contract slightly thus reducing the effective internal diameter ofthe bore distal portion 30 and the aperture 100 reduces stress risersduring flexing.

Preferably the rivet 66 and plate 76 are formed of a bioabsorablematerial such as a polylactide, such as an 85:15 (mol/mol)poly(lactide-co-glycolide) copolymer. More preferably, the rivet 66 isformed of PLLA and the plates are formed of 50/50 D, LPLA blended with95/5 PCL/PDO in a 91:9 ratio as more fully described in U.S. Pat. Nos.5,641,501 and 5,705,181, incorporated herein by reference. Preferablythe instrument body 12 is formed of a sturdy material such as stainlesssteel, however, many other materials, including polymers, would besuitable. Preferably, the instrument body 12 weighs considerably morethan the piston 14 so as to minimize kick-back as the piston 14 isreleased. The setting pin 32, and especially if the setting pin 32 andpiston 14 are integral, is preferably formed of a hardened steel orstainless steel, but of course many other hardy materials would besuitable for such service. The tray 88 preferably is formed of asuitable polymer, but can also be formed of other materials.

To use the instrument 10, a user grasps the handle 42 and retracts thepiston 14 until the flange 64 of the release mechanism 18 engages theannular groove 54 of the piston 14 and holds the piston 14 in aretracted position. The tip 50 of the instrument 10 is inserted throughone of the slits 97 to capture the plug 72 of one of the rivets 66within the bore distal portion 30. The chamfer 102 eases entry of theplug 72 into the bore distal portion 30 and contraction of the tip 50due to the slit 98 helps the tip 50 grip the plug 72. The rivet 66 isthen placed through one of the plate apertures 82 and into a hole in theskull (not shown) and the rivet applier is held thereagainst with someforce, say 2 pounds force. Pressing the button 58 releases theengagement of the piston 14 and flange 64 allowing the setting pin 32 tomove distally to push against the plug 72 breaking its frangibleconnection to the head 68 and driving it between the leaves 70 therebyspreading the leaves and setting the rivet 66.

FIGS. 12 and 13 illustrate a bone drill 110 which provides a simple andelegant solution to the problem of centering and boring holes in apatient's skull into which the rivets 66 (not shown in FIG. 12) arereceived when applying the cranial plate 76 (also not shown in FIG. 12).The drill 110 comprises an elongated drill bit 112 having a proximal end114 with an attachment surface 116 for attachment to a drill chuck (notshown). Any appropriate attachment surface can be substituted therefor.For instance, a two-piece cap (not shown) can be employed which fitsinto the tube instead of using a right and left half as shown. A distalend 118 of the drill bit 112 carries helical cutting edges 120, butother forms of cutting surfaces as appropriate can be substitutedtherefor. A first radial flange 122 extends radially outwardly from thedrill bit 112 and a second larger radial flange 124 extends radiallyoutwardly from the drill bit 112 proximal of the first radial flange122. A pair of windows it 123 allow debris from the drilling to exit thedrill 110 and are arranged so as to release the debris before it canreach and possibly interfere with operation of the spring 140.

A tubular housing 126 having an axial bore 128 therethrough coaxiallyreceives the drill bit 112 through the axial bore 128. A proximal end130 of the housing 126 abuts the second radial flange 124 and therebylimits distal movement of the drill bit 112 through the housing 126. Afirst diameter 132 of the bore 128 at the housing proximal end 130closely matches the diameter of the drill bit 112 for slidingengagement. A central diameter 134 of the bore 128 closely matches thediameter of the first radial flange 122 for sliding engagement. A distaldiameter 136 of the bore 128 closely matches the diameter of the drillbit 112 for sliding 30 engagement, and the change in diameter of thebore 128 between the central diameter 134 and distal diameter 136 formsa radial abutment 138. A coil spring 140 encircles the drill bit 112 andoperates between the abutment 138 and the first radial flange 122 tourge the housing distally along the drill bit 112.

A distal end 142 of the housing 126 carries a chamfer 144 of matchingangle to the chamfer of the holes 82 in the cranial plate 76 (see FIG.6). By pressing the distal end 142 into the chamfered hold 82 the drillbit 112 is centered within the hole 82 allowing accurate drilling.Abutment of the second radial flange 124 and the housing proximal end130 limits travel of the drill bit 112 out of the housing 126 and thuslimits the depth of a hole created by the drill bit 112.

While the invention has been described with regard to a particularembodiment thereof, those skilled in the art will understand, of course,that the invention is not limited thereto since modifications can bemade by those skilled in the art, particularly in light of the foregoingteachings. Reasonable variation and modification are possible within theforegoing disclosure of the invention without the departing from thespirit of the invention.

1. An instrument for applying a surgical fastener, the instrumentcomprising: an elongated body having proximal and distal ends; a pistonaxially moveable within a bore within the body, the piston having adistal end adjacent the body distal end; and a slit through the body tothe bore, the slit extending a distance axially from the body distalend, the slit has a distal end at the body distal end, and an oppositeproximal end, the proximal end of the slit opening into an aperturewider than the slit whereby to reduce stress on the body at the slitproximal end; wherein the bore at the body distal end is sized to snuglyreceive a portion of the fastener therein, the slit allowing the body tocompressively hold said portion of the fastener.
 2. An instrumentaccording to claim 1 wherein the inside diameter of the bore prior tocutting the slit is about 0.0595 inches and the slit is about 0.014inches wide.
 3. An instrument according to claim 1 and furthercomprising a spring urging the piston toward the body distal end and areleasable catch on the body for restraining distal movement of thepiston whereby release of the catch allows the spring to move the pistondistally to impact and apply the surgical fastener.
 4. A method ofholding a surgical fastener within an instrument for applying saidfastener, the method comprising the steps of: providing an instrumentcomprising an elongated body having proximal and distal ends, a pistonaxially moveable within a bore within the body, the piston having adistal end adjacent the body distal end, and a slit through the body tothe bore, the slit extending a distance axially from the body distalend, the slit has a distal end at the body distal end, and an oppositeproximal end, the proximal end of the slit opening into an aperturewider than the slit whereby to reduce stress on the body at the slitproximal end; and pushing a portion of the fastener into the bore at thebody distal end, the body contracting about portion of the plug to holdthe plug within the body.
 5. The method of claim 4 and furthercomprising moving the piston distally to engage and apply the fastener.6. The method of claim 5 wherein the fastener comprises a plurality ofaxially extending leaves and a cylindrical plug adjacent thereto and themethod further comprising the step of pushing the plug with the pistonbetween the leaves to spread the leaves and expand the fastener.
 7. Themethod of claim 6 wherein the fastener is formed of a bioabsorbablematerial.
 8. The method of claim 5 further comprising the step ofrestraining distal movement of the piston with a releasable catch andurging the piston distally with a spring and then releasing the catch todrive the piston distally with the spring.